Hi there!
First we need to remember the following.

Now substitute both of the formulas.

Work out the parenthesis.

And finally collect terms.

~ Hope this helps you!
Answer:
15
Step-by-step explanation:
1 dime = 10
1 quarter=25
x=number of coins - dimes
y= number of coins - quarters
x (10)+y(25)=10.25
x+y=50
x= 50-y
x(10)+y(25)=1025
(50-y)(10)+25y =1025
500-10y+25y=1025
500+15y=1025
15y= 1025 - 500
15y=525
y=525/15
y=35
x= 50-35=15
40 + 10x = 5x - 30
To begin isolating x, subtract 40 from both sides.
40 + 10x - 40 = 5x - 30 - 40
10x = 5x - 70
Subtract 5x from both sides.
10x - 5x= 5x - 70 - 5x
5x = -70
Finally, divide both sides by 5.
5x/5 = -70/5
x = -14
Answer:
x = -14
1) Expand by distributing terms
7a+7 x-3
Simplify 7x-3 to -21
7a-21